KR20090010718A - Power supply circuit of back light unit for liquid crystal display - Google Patents

Power supply circuit of back light unit for liquid crystal display Download PDF

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Publication number
KR20090010718A
KR20090010718A KR1020070074054A KR20070074054A KR20090010718A KR 20090010718 A KR20090010718 A KR 20090010718A KR 1020070074054 A KR1020070074054 A KR 1020070074054A KR 20070074054 A KR20070074054 A KR 20070074054A KR 20090010718 A KR20090010718 A KR 20090010718A
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KR
South Korea
Prior art keywords
power supply
backlight
liquid crystal
power
transformer
Prior art date
Application number
KR1020070074054A
Other languages
Korean (ko)
Inventor
윤창선
Original Assignee
엘지이노텍 주식회사
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 엘지이노텍 주식회사 filed Critical 엘지이노텍 주식회사
Priority to KR1020070074054A priority Critical patent/KR20090010718A/en
Publication of KR20090010718A publication Critical patent/KR20090010718A/en

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    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHTING NOT OTHERWISE PROVIDED FOR
    • H05B41/00Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14Circuit arrangements
    • H05B41/26Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • H05B41/28Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
    • H05B41/282Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02BCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00Energy efficient lighting technologies
    • Y02B20/16Gas discharge lamps, e.g. fluorescent lamps, high intensity discharge lamps [HID] or molecular radiators
    • Y02B20/18Low pressure and fluorescent lamps
    • Y02B20/183Specially adapted circuits

Abstract

The present invention relates to a backlight unit power supply circuit of a liquid crystal display device.
The present invention provides at least two backlights; Power supply paths respectively supplying power to the backlight; And a current deviation compensation unit of the at least two power supply paths connected to the power supply path whose length is shorter than that of other paths.
According to the present invention, the ratio of the power supplied to the backlight on the side with high leakage current and the backlight on the side with low leakage current can be kept the same, so that the luminance deviation of the backlight unit caused by the power deviation can be improved. .

Description

Backlight unit power supply circuit for liquid crystal display device {POWER SUPPLY CIRCUIT OF BACK LIGHT UNIT FOR LIQUID CRYSTAL DISPLAY}

1 is a plan view briefly showing a power supply structure of the ONE-BOARD backlight unit.

2 is a block diagram schematically showing a configuration according to an embodiment of the present invention.

3 is a circuit diagram showing in more detail the configuration according to an embodiment of the present invention.

<Description of Signs of Major Parts of Drawings>

10: power supply circuit 11: path 1

12: path 2 13: current deviation compensation unit

D: liquid crystal display device T1, T2: transformer 1,2

CON1 ~ CON4: Connector 1 ~ 4 W1, W2: Electric wiring 1,2

C1, C2: Capacitor1,2 R1: Register1

The present invention relates to a backlight unit power supply circuit of a liquid crystal display device.

In general, liquid crystal display devices are currently used in almost all information processing equipment that requires a display device.

The liquid crystal display device has an optical property such as birefringence, photoreactivity, dichroism, and light scattering characteristics of a liquid crystal cell that applies a voltage to a specific molecular array of liquid crystals, converts it into another molecular array, and emits light by the molecular array. It is a display device that uses the modulation of light by a liquid crystal cell by converting the change of the light into a visual change.

Since the liquid crystal display is a light receiving element that does not emit light by itself, the liquid crystal panel is illuminated by using a backlight unit attached to the rear side of the liquid crystal panel. The light transmittance of the liquid crystal panel is adjusted according to an applied electrical signal, and a still image or a moving image is correspondingly represented on the liquid crystal panel.

As a lamp used in the backlight unit for supplying light to the liquid crystal panel as described above, a cold cathode fluorescent lamp (CCFL) is generally used.

The cold cathode fluorescent lamp is lit on the same principle as the hot cathode fluorescent lamp (Hot Cathode Fluorescent Lamp), which is a fluorescent lamp commonly known to us. It turns on as the electron emission by the applied electric field, and shows a difference that the amount of heat generated is very small.

The backlight unit of the liquid crystal panel operates according to a signal (power) supplied through an inverter.

In recent years, as a liquid crystal display device becomes large, a backlight is installed at both ends of the liquid crystal display device. In this case, the inverter is implemented in a TWO-BOARD method (a method in which one PCB is provided for each master and slave).

However, for the volume reduction and the price competitiveness of the liquid crystal display device (D), the newly proposed inverter is a circuit of the ONE-BOARD method (Master, Slave) to one PCB (P) as shown in the accompanying drawings. Implementation).

The problem with the ONE-BOARD type inverter is that as the PCB (P) is installed on one side of the panel (now installed mainly on the master side), the current on the other side is transmitted to the other backlight (L2) via the electrical wiring. In addition, there is a problem in that a current is leaked to the panel and the current delivered to the lamp is reduced.

As a result, a deviation occurs in the current between the master and the slave, and the current deviation of the lamp makes the brightness between the backlights different. This leads to a luminance deviation of the backlight unit, resulting in an uneven output screen of the liquid crystal display.

The present invention can improve the luminance deviation of the backlight unit caused by the power deviation.

The present invention provides at least two backlights; Power supply paths respectively supplying power to the backlight; And a current deviation compensation unit of the at least two power supply paths connected to the power supply path whose length is shorter than that of other paths.

On the other hand, the plurality of power supply path of the present invention includes a transformer for transforming the input power; A connector for connecting the power output from the transformer to an external backlight; Another connector connected to the connector may be provided at one end, and may include an electric wiring connecting the backlight and the transformer.

In this case, the transformer and the connector are designed and arranged on the PCB, the PCB may be installed on one end of the liquid crystal display device.

In addition, one of the electrical wiring of each path may be provided longer than the other.

On the other hand, in the present invention, the current deviation compensation unit is configured to include a device that is connected to the ground in parallel with the ground between the connector and the secondary side of the transformer of the short path of the electrical wiring in each of the path to branching the power supply (leak) Can be.

In this case, the current deviation compensation unit may include a pair of capacitors connected in series between the secondary side and the ground of the transformer and a resistor connected in parallel with the ground side of the capacitor.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram schematically showing a configuration according to an embodiment of the present invention, Figure 3 is a circuit diagram showing a configuration in more detail according to an embodiment of the present invention.

2 and 3, the power supply circuit for the backlight (L1) (L2) for respectively irradiating light is installed on the rear end portions of the liquid crystal display device that does not emit light by the pixel itself In (10), the length of the electrical wiring is relatively long among the power supply paths 1 and 2 (11) and 12 of the power supply circuit 10 for supplying power to the backlights L1 and L2 at both ends. It includes a current deviation compensator 13 which induces intentional leakage in a power supply path having a short leakage current.

Meanwhile, in the present invention, the paths 1 and 2 (11) and 12 are respectively transformers 1 and 2 (T1) (T2) for transforming an input power source; Connectors 1 and 2 (CON1) and CON2 for connecting the power output from the transformers 1 and 2 (T1) and T2 to the external backlights 1 and 2 (L1) and L2; Other connectors 3 and 4 (CON3) and CON34 connected to the respective connectors 1 and 2 (CON1) and CON2 are provided at one end thereof, and the backlights 1 and 2 (L1) and L2 and transformers 1 and 2 (T1). It comprises a electrical wiring 1, 2 (W1) (W2) connecting the (T2).

In this case, the power output from the switching unit (MOS-FET) is applied to the primary sides of the transformers 1 and 2 (T1) and (T2), so that the transformers 1 and 2 (T1) and T2 are respectively input. The power is transformed and output to the secondary side.

Then, the output power is connected to the electrical wiring 1, 2 (W1) (W2) via the connectors 1, 2 (CON1) (CON2) and the connectors 3, 4 (CON3) (CON4), respectively. Turn on L1) and L2 respectively.

In this case, the transformers 1 and 2 (T1) and T2 and the connectors 1 and 2 (CON1) and CON2 are designed and arranged on a PCB, and the PCB is installed at one end of the liquid crystal display.

In addition, each of the electric wirings 1 and 2 (W1) and W2 of the path 1 (11) and the path 2 (12) is provided longer than the other one. The reason for this is that the backlights 1 and 2 (L1) and L2 are respectively provided at both ends of the liquid crystal display, and the PCB is installed in the backlight portion of one of the backlights 1 and 2 (L1) and L2.

On the other hand, the current deviation compensation unit 13 of the present invention is connected in parallel with the ground between the connector and the secondary side of the transformer of the path of the shorter electric wiring of the path 1 (11) and the path 2 (12) power supply It includes a device for branching (BRANCHING) to leak.

At this time, the length of the electric wiring is one embodiment, the length of the electric wiring connecting the backlight 2 (L2) is longer.

Here, the current deviation compensation unit 13 is a pair of capacitors 1, 2 (C1) (C2) and a ground-side capacitor 2 (C2) of the capacitor connected in series between the secondary side of the transformer and the ground in one embodiment And a resistor (R1) connected in parallel with.

At this time, the current deviation compensation unit 13 is included in the path 1 (11) having a short length of the electrical wiring.

In this case, the current deviation compensator 13 changes the flow of current, which is a power output from the secondary side of transformer 1 (T1).

That is, since the current from the secondary side of the transformer 1 (T1) flows to the connector 1 (CON1) side and partly flows to the current deviation compensator 13 to ground, the current output through the connector 1 (CON1) Will be reduced.

Therefore, the current applied to the backlight 1 (L1) side is output smaller than the current applied to the backlight 2 (L2) side. However, the current output high toward the backlight 2 (L2) side is reduced in the process of passing through the electrical wiring 2 (W2), that is, the high voltage connection, so that the backlight 2 (L2) applies the same current value as the backlight 1 (L1). Light up to have the same brightness.

For example, suppose that 100 currents are respectively applied to the backlight 1 L1 and the backlight 2 L2 to have the same brightness. In this case, the electrical wiring W2, which is a path for providing the current to the backlight 2 L2, is provided. When the leakage current from the device is 30, a current of 130 is supplied from the transformer to the backlight 1 (L1) and the backlight 2 (L2), respectively.

Then, as described above, the backlight 2 L2 leaks a current of 30 via the electrical wiring 2 W2, and as a result, a current of 100 is applied to the backlight 2 L2.

On the other hand, in the backlight 1 (L1), a pair of capacitors 1, 2 (C1) (C2) constituting the current deviation compensation unit 13 and a resistor (R1) connected in parallel with the ground-side capacitor 2 (C2) of the capacitors. Each time constant (capacitance) of 130 provides a current of 130 down (intentionally down).

As a result, the same current is applied to the backlight 1 (L1) and the backlight 2 (L2) to improve the luminance deviation of the backlight unit.

In this case, the luminance deviation between the backlight 1 L1 and the backlight 2 L2 may be adjusted by adjusting the capacitance value of the current deviation compensator 13. Therefore, it is preferable that the capacitors 1, 2 (C1) (C2) and resistor 1 (R1) of the current deviation compensator 13 are variable elements.

While the invention has been described and illustrated in connection with a preferred embodiment for illustrating the principles of the invention, the invention is not limited to the configuration and operation as such is shown and described.

Rather, those skilled in the art will appreciate that many modifications and variations of the present invention are possible without departing from the spirit and scope of the appended claims.

Accordingly, all such suitable changes and modifications and equivalents should be considered to be within the scope of the present invention.

According to the present invention, the PCB is intentionally used in a power supply path having a relatively low leakage current in the One-Board method, in which a length of a wiring, which is a path for supplying power to a backlight installed at one end and supplying power to a backlight installed at the other end, is long. Including a current deviation compensator for inducing a leakage current, the ratio of the power supplied to the backlight on the side with a high leakage current and the backlight on the side with a small leakage current can be kept the same, and the backlight unit generated by the power deviation Can improve the luminance deviation.

Claims (5)

  1. At least two backlights;
    Power supply paths respectively supplying power to the backlight; And
    And a current deviation compensator connected to a power supply path of which the length of the path is shorter than other paths among the at least two power supply paths.
  2. The method of claim 1, wherein each power supply path is
    A transformer for transforming an input power source;
    And a connector for connecting the power output from the transformer to the backlight at one end thereof, the electrical wiring connecting the backlight and the transformer to the power supply circuit of the liquid crystal display device.
  3. The method of claim 2, wherein the current deviation compensation unit
    And a ground side connected in parallel with a ground side between a secondary side of a transformer included in a power supply path having a length shorter than other paths and the connector.
  4. The method according to any one of claims 1 to 3,
    And the current deviation compensating part includes a device for leaking power.
  5. The method of claim 4, wherein the current deviation compensation unit
    And a pair of capacitors connected in series between the secondary side and the ground of the transformer and a resistor connected in parallel with the ground side capacitor among the capacitors.
KR1020070074054A 2007-07-24 2007-07-24 Power supply circuit of back light unit for liquid crystal display KR20090010718A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
KR1020070074054A KR20090010718A (en) 2007-07-24 2007-07-24 Power supply circuit of back light unit for liquid crystal display

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
KR1020070074054A KR20090010718A (en) 2007-07-24 2007-07-24 Power supply circuit of back light unit for liquid crystal display
US12/178,068 US7859195B2 (en) 2007-07-24 2008-07-23 Apparatus for controlling lamp driving and light unit having the same

Publications (1)

Publication Number Publication Date
KR20090010718A true KR20090010718A (en) 2009-01-30

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Application Number Title Priority Date Filing Date
KR1020070074054A KR20090010718A (en) 2007-07-24 2007-07-24 Power supply circuit of back light unit for liquid crystal display

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KR (1) KR20090010718A (en)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5400667B2 (en) * 2010-03-10 2014-01-29 富士重工業株式会社 Driving device for field emission lamp
DE102010023928A1 (en) * 2010-06-09 2011-12-15 Minebea Co., Ltd. Electric circuit for operating lamp with alternating current source for backlight unit of LCD in flat TV, has pattern lamp secondary winding connected with high impedance ground connections
US10003194B2 (en) 2014-10-24 2018-06-19 Enphase Energy, Inc. Parallel battery system

Family Cites Families (5)

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Publication number Priority date Publication date Assignee Title
JP2004349040A (en) * 2003-05-21 2004-12-09 Nec Lcd Technologies Ltd Backlight device and liquid crystal display
US7187139B2 (en) * 2003-09-09 2007-03-06 Microsemi Corporation Split phase inverters for CCFL backlight system
JP2005353572A (en) * 2004-05-13 2005-12-22 Sony Corp Fluorescence tube driving device, and liquid crystal display device
KR101159356B1 (en) * 2005-12-12 2012-06-25 엘지디스플레이 주식회사 Apparatus For Driving Back Light of Liquid Crystal Displa
KR101233819B1 (en) * 2006-02-07 2013-02-18 삼성디스플레이 주식회사 Apparatus for driving lamp and liquid crystal display having the same

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US20090026971A1 (en) 2009-01-29
US7859195B2 (en) 2010-12-28

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